Electrostatic duplicating process

ABSTRACT

An electrostatic duplicating method in which a receptor sheet is collated with a transfer sheet which has a backing of transferable coating material on one surface and causing at least a partial transfer of the coating to the receptor sheet by pressure or other means to thereby form electrical conductivity differences between imaging and background areas on each surface, one of the sheets being then placed into contact with a dielectric recording member and an electrical field applied therethrough to charge the dielectric surface of the recording member patternwise due to the electrical conductivity differences caused by the transferable coating which recording member can then have the image made visible by applying a developer which is sensitive to the electrical pattern.

United States Patent Wright 1451 Aug. 19, 1975 1 ELECTROSTATIC DUPLICATING PROCESS [75] Inventor: Robert J. Wright, Tranmere,

Australia [73] Assignee: Research Laboratories of Australia Pty. Limited, Eastwood, Australia [22] Filed: Dec. 20, 1972 [21] Appl. No.: 316,754

[52] US. Cl. 427/19; 101/D1G. 13; 427/144; 427/146 [51] Int. Cl.. G03g 13/08; 003g 13/10; 603g 13/22 [58] Field of Search 117/3.1, 17.5, 35.5, 36.1, 117/10, 37 LE; 96/1 R, 1 C, 1 S, 1 D, 1.3; lOl/DIG. 13

[56] References Cited UNITED STATES PATENTS I 2.912.586 11/1959 Gundlach 96/1 C 3,109.367 11/1963 Walkup et a1. 117/17.5 3,276,933 10/1966 Brant 117/3.1 3,400,656 9/1968 Thourson 101/1 3,479,953 11/1969 Ritzerfeld..... 117/36.1 3,505,955 4/1970 Ritzerfeld 117/36.1 3,562,003 2/1971 Frohlich 117/355 3,565,612 2/1971 Clark 96/1 M fieve/oper Eal/e/ Primary ExaminerMichae1 Sofocleous Attorney, Agent, or FirmKinzer, Plyer, Dorn & McEachran [5 7] ABSTRACT An electrostatic duplicating method in which a receptor sheet is collated with a transfer sheet which has a backing of transferable coating material on one surface and causing at least a partial transfer of the coating to the receptor sheet by pressure or other means to thereby form electrical conductivity differences between imaging and background areas on each surface, one of the sheets being then placed into contact with a dielectric recording member and an'clectrical field applied therethrough to charge the dielectric surface of the recording member patternwise due to the electrical conductivity differences caused by the transferable coating which recording member can then have the image made visible by applying a developer which is sensitive to the electrical pattern.

2 Claims, 4 Drawing Figures Deva/o ed /ma /ec /ros [a (la /mqye ELECTROSTATIC DUPLICATING PROCESS This invention relates to duplicating, and in particular relates to means whereby duplicate copies of information may be produced using a master sheet to control the charging of the dielectric surface of an electrographic recording member under the influence of an externally applied electrostatic field.

Various prior art short run duplicating methods are known, such as hectographic printing in which a master is prepared by typing or writing or drawing on a paper sheet with the back surface of the sheet in contact with a pnssure transferable layer on a tissue or the like, whereby a reverse reading image deposit consisting of pressure transferred material is formed on the back surface of the master. Such pressure transferred material contains coloring matter which is usually an alcohol soluble dye. When such pressure transferred material is contacted with a further paper surface which has been wetted with alcohol a portion of the dye image is dissolved by the alcohol and forms a right reading image on the surface of the second sheet. This process can be repeated to produce a multiplicity of copies, up to about 100 if desired.

Electrostatic printing methods are also known, in which electrostatic latent images are produced on dielectric surfaces and developed thereon by the application of dry or liquid dispersed electroscopic marking particles, and in some instances the dielectric properties of such dielectric surfaces are changed by the action of light, in which case photoconductors are contained within the dielectric coating. In other instances the dielectric surfaces are insulating films which are not light sensitive, but are selectively charged by the application of electric pulses to writing styli in contact with the dielectric surface. It is also known to image dielectric surfaces by pressure means in patterned form, whereby compacting of the dielectric layer or deformation of the layer or particle or ionic migration or the like in patterned form produces a latent image which may be developed by the application to the surface of the aforementioned electroscopic marking particles.

In the past it also has been known to control the charging of a dielectric surface by placing a mask on said surface. Such masks have for example consisted of metal stencils with cut out portions corresponding to the information to be reproduced. When an electrographic sheet is positioned with its backing member in contact with a grounded base member, and the stencil carrying the cut out information to be reproduced is positioned between the dielectric surface of the electrographic sheet and a corona generating means, the application of corona producing voltage to the corona generating means causes the production of an electrostatic latent image on the dielectric surface corresponding to the cut out portions of the stencil. The stencils used may be cut from a variety of materials in addition to metal, and may be conducting or insulating as desired. Generally the information to be reproduced consists of holes which penetrate completely through the stencil and allow the passage of ions or charged gas molecules whereby the latent image charge is produced on the dielectric surface.

The prior art processes described suffer from several disadvantages in relation to multiple copy reproduction. For instance hectographic masters are fragile and easily damaged, and are not capable of producing high resolution copies. Electrostatic methods require either expensive equipment or elaborate master making techniques when photoconductive materials are not used, and when photoconductive recording elements are employed these are relatively expensive and relatively heavy. The equipment is also elaborate and relatively expensive. The processes involving the use of stencils suffer from the disadvantage that closed characters cannot be cut out completely, and thus the latent electrostatic image and subsequent developed image contain distorted characters. In addition such stencils are generally produced using relatively rigid materials which require machine cutting and cannot be cut using a typewriter or other simple means. Thus electrostatic duplicating using cut stencils is not readily adapted to office systems using normal office equipment such as typewriters or the like.

We have now found that a duplicating master can be prepared using simple means such as handwriting or drawing or typewriting or the like in a manner similar to that used for preparing hectographic masters, and the so formed duplicating master may be used to control the charging of the dielectric surface of an electrographic recording member in contact with said master to form an electrostatic latent image on the dielectric surface of such recording member in a similar manner as previously referred to in relation to machine cut stencils. The so formed electrostatic latent image may then be developed by application of dry or liquid dispersed electroscopic marking particles, such as the toners commonly employed in electrophotographic office copying machines and the like. Further such masters can be prepared to produce copies of high contrast with sharper edge definition than is possible using hectrographic printing methods, and longer printing runs can be produced from such masters than from hectographic masters as the image forming step does not remove material from the master surface.

In this present invention the duplicating master is prepared by coating a transferable layer on a suitable backing such as paper or the like, and transferring the said transferable coating imagewise to another surface by typing or handwriting or other means as desired. The so produced duplicating master may be either the coated sheet from which the coating has been removed imagewise by transfer, or alternatively the receptor sheet to which the transferable coating was transferred imagewise may form the duplicating master, depending on the composition of the transferable coating. Generally in those instances in which the electrical conductivity of the transferable coating is greater than that of the backing member the transferred material allows the dielectric surface of an electrographic recording member contacting said coating to become charged under the influence of an applied electrostatic field, whereas in those instances in which the transferable coating is of lower conductivity than areas of the backing relatively free from such coating, charging of the dielectric surface of the electrographic recording members occurs in those areas contacting free areas of the master.

Thus the present invention describes a master sheet for use in an electrostatic duplicating process in which electrical conductivity differences are set up between imaging and background areas on said master to allow selective charging of the dielectric surface of a recording member in nominal contact with the master under the influence of an applied electrostatic field, and

wherein said master sheet comprises a backing having a transferable coating on one side thereof in patterned form defining the image to be duplicated, and wherein the electrical conductivity of the imaging areas of said master is higher than the electrical conductivity of the background areas of said master.

In order to carry out the present invention a transferable coating is produced on one surface of a first sheet of paper or the like, and brought into contact with one surface of a second sheet of paper. When for instance pressure is applied to the sandwich by drawing or writing or typing the transferable coating is transferred to the surface of the second sheet of paper in those areas to which for instance pressure was applied. When the two sheets are separated it is found that on the coated surface of the first sheet the coating deposit has been removed imagewise and an imagewise coating deposit has been formed on the surface of the second sheet. Provided the composition of the transferable coating has been correctly chosen either the first or the second sheet may be used as a master to control the charging of a dielectric surface contacted with said imaged master surface simultaneously with the application of an electrostatic field.

In those instances where it is desired to use the second sheet as the master, hereinafter referred to as Embodiment 1, it has been found advantageous to provide conductive additives in the transferable coating in order to facilitate the subsequent imagewise charging of a dielectric surface contacted thereto, whereas in those instances when the first sheet is used as a master, hereinafter referred to as Embodiment 2, it is advantageous to prepare a transferable coating which is substantially free of such conductive additives in order to confine the charging of the dielectric surface of those areas in contact with areas on the master surface from which the pressure transferable coating has been removed or at least substantially reduced in thickness.

While not wishing to be bound to any theory, it appears possible that the conductive additives in the imaging areas of the master in Embodiment l, facilitate the selective charging of those areas of the dielectric surface which are in contact with the imaging areas of the master, whereas in Embodiment 2 the relatively insulating background areas of the master inhibit charging of the background areas of a dielectric surface in contact with said master, charging of the dielectric surface being substantially limited to those areas which correspond to .the imaging areas on the master from which the pressure transferable insulating coating has been removed.

In each of Embodiments l and 2 the transferable coating may consist of a wax or the like such as a paraffin wax or microcrystalline wax or synthetic wax or the like, and whereas in Embodiment 2 it is preferable that any release additives should be insulating, such as mica or the like. In Embodiment 1 it is advantageous to add conductive additives to the wax before coating. Such additives may include cetyl alcohol, alkylarly 1:4 sulphonic acid, dodecylbe'nzene-sulphonic acid sodium salt, di-iso-butyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride monohydrate, sodium di-octyl sulphosuccinate, octyl phenol ethoxylates, zirconium octoate, calcium stearate and the like, such additives usually being present in a quantity of l-50% based on the weight of wax or other pressure transferable binder.

In each embodiment the image bearing surface of the master is contacted with the dielectric surface of an electrographic recording member and the sandwich passed through a charging device, such as a corona charging device of the type used in office copying machines and the like. When corona charging devices are used the applied charging voltage is preferably within 3 KV 7 KV. Alternatively rollers may be used to provide contacting means and such rollers may have a charging voltage applied thereto, in which instance lower charging voltages may usually be used, such as 200 volts 4 KV. For convenience the master may be mounted to a drum and the dielectric surface of the electrographic recording member contacted to the surface of the master during charging, after which the electrographic sheet is passed through a developing device such as those used in electrophotographic office copying machines and the like. Such apparatus may be motor driven or hand operated as desired, and may thus be a simple apparatus similar to a hectographic duplicator to which has been added charging and developing means.

It will be realised from the foregoing that a differential pattern is produced on an electrographic recording member which can be developed and that the master sheet which modifies the dielectric sheet in a field, which can be the sheet with the pressure transferable layer or the receptor sheet, can be re-used any number of times.

As one example, the basis of the invention is illustrated as a pressure imaging method in the accompanying drawings by enlarged fragmentary views which are not to scale and in which;

FIG. 1 shows a receptor sheet in contact with a sheet having a pressure transferable backing, showing pressure being applied at three areas,

FIG. 2 shows the result of the pressure application when the receptor sheet is removed from the transfer sheet to produce the two usable masters.

FIG. 3 shows the master in this case the receptor sheet, placed into contact with a dielectric recording member and being patterned electrically by passing it between rollers to which a voltage is applied and,

FIG. 4 shows how the dielectric recording member can then be developed by passing it, for instance, between a developer roller and a pressure roller.

This, of course, is not illustrative of the general principle and it will be realised that variations can be effected in the mechanism, but in the illustrated form the sheet with the pressure transferable layer is designated 1, the pressure transferable layer A, the receptor sheet 2, the pressure members 3, the electrographic recording member 4, the dielectric layer on it B, the voltage applying rollers 6 and 7, the charging device 8, the developer and pressure rollers respectively 9 and 10, the developed areas on the electrographic recording member 4 being indicated by 11 while the image charge is indicated by 12. As will be realised pressure imaging is only one form of the invention.

In order that the invention may be more fully understood, reference will now be made to the followingexamples which illustrate each embodiment. However, it will be realised that the materials and proportions herein disclosed are illustrative only of the principle of the invention and should not be read in the sense of limiting the scope of the invention.

The following examples will serve to illustrate the first embodiment of this invention in which co rductive additives are included in the pressure transferable coating and transferred imagewise to the master sheet by pressure transfer means normally as wrong way reading copy.

EXAMPLE 1 A transferable coating was prepared using the following materials.

Microcrystalline wax, mp l60l80C g Dodecylbenzinc sulphonic acid sodium salt 3 g Water 5 g Butanol 100 g Toluol 100 g These materials were mixed together to form a homogenous solution, and coated on a bank weight bond paper to form a dry coating of about 5 grrn. substance.

The duplicating master was prepared by contacting the coated surface of the so prepared tissue with the dielectric surface of a polyvinyl butyral coated paper sheet, and typing thereon to transfer an imagewise conductive waxy deposit to the insulating surface of the master sheet. The image bearing surface of the master sheet was then placed in nominal contact with the dielectric surface of an electrographic recording member and the two sheets passed through the corona charging device of an office copying machine. The dielectric surface of the electrographic recording member was then developed in a liquid dispersed toner of the type used in electrophotographic office copying machines and the like. A high contrast high density positive reproduction of the original was produced. The process is found to be repeatable many time to produce any desired number of copies up to several hundred.

EXAMPLE 2 The dodecylbenzine sulphonic acid sodium salt of Example 1, which was the major conductive constituent of the dried waxy film, was replaced with anionic benzyl ammonium chloride monohydrate.

EXAMPLE 3 The dodecylbenzine sulphonic acid sodium salt of Example 1 was replaced with alkylaryl l4 sulphonic acid.

EXAMPLE 4 A pressure transferable coating was prepared as follows:

Parafiin wax 20 g Cetyl alcohol 20 g Calcite 20 g Alkylaryl 1-4 sulphonic acid 2 g Toluol 50 g Butanol 50 g This formulation was ball milled to obtain a uniform dispersion of the calcite, and coated on a light weight manifold paper. The master was prepared by imagewise transfer of this coating to the polyvinyl butyral coated surface of a coated paper sheet. This master was also used as in Example 1.

EXAMPLE 5 The following tissue coating formulation was prepared and used as in Example 1.

Microcrystalline wax 30 g Petroleum jelly 5 g Whiting 25 g l,l,l. trichlorocthanc lOO g EXAMPLE 6 A coating was prepared consisting of Microcrystalline wax Toluol The wax was dissolved in the toluol and coated on a thin manifold paper sheet. This coated sheet was prepared for use as aduplicating master by pressure transfer of wax from the image areas to another surface in this case to a bond paper sheet which was subsequently discarded. The relatively wax-free imaging areas of the so formed master allowed the dielectric surface of an electrographic recording member to become charged under the conditions as described in relation to Example 1, while the remaining wax deposit in the background areas prevented charge build up in those areas of the dielectric surface in nominal contact with the waxy areas of the master.

EXAMPLE 7 The master of Example 6 was somwhat tacky to handle. This defect was over come by the addition of 10g of 400 mesh mica to the coating formulation of Example 6.

EXAMPLE 8 and 9 The microcrystalline wax of Example 6 and 7 was replaced with paraffin wax.

EXAMPLE 10 A coating formulation was prepared as follows:

Montan wax 10 g 400 mesh mica l0 g Toluene 50 g These components were hot milled together and coated on a manifold paper sheet. This sheet was used as a duplicating master as in Example 6.

I claim:

1. An electrostatic duplicating process consisting essentially of the following steps:

a. collating a paper substrate as a receptor sheet with a paper substrate as transfer sheet, said transfer sheet comprising a backing and transferable coating material on one surface thereon, the transferable coating consisting essentially of a wax material containing conductive particles having a pre-selected electrical conductivity character;

b. transferring by pressure transfer part of said transfer able coating material to said receptor surface to thereby form electrical conductivity differences between image and background areas on said receptor sheet contacting surface;

c. separating-said sheets;

d. contacting the thus imaged surface of the receptor sheet so formed as a master with the dielectric surface of a dielectric recording member simultaneous with application of an electric field therethrough to produce an electrostatic latent image on said dielectric surface of the recording member in accordance with electrical conductivity differences of said receptor sheet master;

e. separating said receptor sheet master and said dielectric recording member;

f. developing said latent image to produce a copy on said dielectric surface by the attraction thereto of electroscopic marking particles; and

g. re-using the receptor sheet master in steps (d) and (e) for at least one additional copy under step (f). 2. An electrostatic duplicating process consisting essentially of the following steps: a. collating a paper substrate as a receptor sheet with a paper substrate as a transfer sheet, said transfer sheet comprising a backing and transferable coating material on one surface thereon, the transferable coating consisting essentially of an insulating wax having a pre-selected electrical conductivity character;

b. transferring by pressure transfer part of said transferable coating material to said receptor surface to thereby form electrical conductivity differences between image and background areas on said transfer sheet contacting surface;

c. separating said sheets;

d. contacting the thus imaged surface of the transfer sheet so formed as a master with the dielectric surface of a dielectric recording member simultaneous with application of an electric field therethrough to produce an electrostatic latent image on said dielectric surface in accordance with electrical conductivity differences of said transfer sheet master;

e. separating said transfer sheet master and said dielectric recording member;

f. developing said latent image to produce a copy on said dielectric surface by the attraction thereto of electroscopic marking particles; and

g. re-using the transfer sheet master in steps (d) and (e) for at least one additional copy under step (f).- 

1. AN ELECTROSTATIC DUPLICATING PROCESS CONSISTING ESSENTIALLY OF THE FOLLOWING STEPS: A. COLLATING A PAPER SUBSTRATE AS A RECEPTOR SHEET WITH A PAPER SUBSTRATE AS TRANSFER SHEET, SAID TRANSFER SHEET COMPRISING A BACKING AND TRANSFERABLE COATING MATERIAL ON ONE SURFACE THEREON, THE TRANSFERABLE COATING CONSISTING ESSENTIALLY OF A WAX MATERIAL CONTAINING CONDUCTIVE PARTICLES HAVING A PRESELECTED ELECTRICAL CONDUCTIVITY CHARACTER, B. TRANSFERRING BY PRESSURE TRANSFER PART OF SAID TRANSFERABLE COATING MATERIAL TO SAID RECEPTOR SURFACE TO THEREBY FORM ELECTRICAL CONDUCTIVITY DIFFERENCES BETWEEN IMAGE AND BACKGROUND AREAS ON SAID RECEPTOR SHEET CONTACTING SURFACE, C. SEPARATING SAID SHEETS, D. CONTACTING THE THUS IMAGED SURFACE OF THE RECEPTOR SHEET SO FORMED AS A MASTER WITH THE DIELECTRIC SURFACE OF A DIELECTRIC RECORDING MEMBER SIMULTANEOUS WITH APPLICATION OF AN ELECTRIC FIELD THERETHROUGH TO PRODUCE AN ELECTROSTATIC LATENT IMAGE ON SAID DIELECTRIC SURFACE OF THE RECORDING MEMBER IN ACCORDANCE WITH ELECTRICAL CONDUCTIVITY DIFFERENCES OF SAID RECEPTOR SHEET MASTER, E. SEPARATING SAID RECEPTOR SHEET MASTER AND SAID DIELECTRIC RECORDING MEMBER, F. DEVELOPING SAID LATENT IMAGE TO PRODUCE A COPY ON SAID DIELECTRIC SURFACE BY THE ATTRACTION THERETO OF ELECTROSCOPIC MARKING PARTICLES, AND G. RE-USING THE RECEPTOR SHEET MASTER IN STEPS (D) AND (E) FOR AT LEAST ONE ADDITIONAL COPY UNDER STEP (F).
 2. An electrostatic duplicating process consisting essentially of the following steps: a. collating a paper substrate as a receptor sheet with a paper substrate as a transfer sheet, said transfer sheet comprising a backing and transferable coating material on one surface thereon, the transferable coating consisting essentially of an insulating wax having a pre-selected electrical conductivity character; b. transferring by pressure transfer part of said transferable coating material to said receptor surface to thereby form electrical conductivity differences between image and background areas on said transfer sheet contacting surface; c. separating said sheets; d. contacting the thus imaged surface of the transfer sheet so formed as a master with the dielectric surface of a dielectric recording member simultaneous with application of an electric field therethrough to produce an electrostatic latent image on said dielectric surface in accordance with electrical conductivity differences of said transfer sheet master; e. separating said transfer sheet master and said dielectric recording member; f. developing said latent image to produce a copy on said dielectric surface by the attraction thereto of electroscopic marking particles; and g. re-using the transfer sheet master in steps (d) and (e) for at least one additional copy under step (f). 